Senate Republicans think President Trump is playing a constructive role in the tax debate and are optimistic about their chances of winning a big legislative victory.

Trump flexed his muscle as an advocate on Capitol Hill Tuesday when he took on Sen. Ron Johnson (R-Wis.) during a private meeting after Johnson threatened the day before to vote against the tax bill.

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Trump also addressed deficit concerns raised by Sens. Bob Corker (R-Tenn.) and James Lankford (R-Okla.), warning them that lawmakers needed to be careful not to hurt future growth by setting up a backstop measure that would raise taxes in case the bill’s growth projections fell short.

The message got through to Johnson and Corker, who were threatening to vote against the tax bill in the Senate Budget Committee.

Both senators voted “yes,” allowing it to pass the panel by a single vote and giving it crucial momentum.

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Senate Republican Whip John Cornyn (Texas) said Trump gave the tax bill a shot of adrenaline.

“I thought the president did a good job of inspiring us all to get the work done,” he said. “This is a political imperative for Republicans.”

“He brought that message home and I thought it resonated,” he said.

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“Tax policy is obviously something he’s worked on a lot for a long time. Just his own personal business dealings and his own taxes so he’s very knowledgeable of this issue,” Lankford said.

He acknowledged that Trump made a good point about the potential of a backstop measure to cause uncertainty in the business sector.

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The president will travel to Missouri on Wednesday to pressure Democratic Sen. Claire McCaskill (Mo.), who faces a tough reelection in 2018, to vote for the bill.

Trump flew to Indiana, the home state of another vulnerable Democrat, Sen. Joe Donnelly, in September to promise “revolutionary change” to the tax code and pledge the economy would take off “like a rocket ship.”

He’s also taken a hands-on approach to lobbying lawmakers in the tax debate, meeting with the entire Senate Republican conference on Capitol Hill just over a month ago to unify it behind his tax plan.